Image processing device, projection system, image processing method, and image processing program

ABSTRACT

An image processing device for a projection system includes an image generation unit and a brightness acquisition unit, and the image generation unit generates data for projecting the specific image, as a first portion in the first data for display, which corresponds to the first superimposed region, generates a second portion in the first data for display, which corresponds to the first non-superimposed region based on first input image data in the data of the projection target image, which corresponds to the first non-superimposed region, and the second brightness, and generates a third portion in the second data for display, which corresponds to the second superimposed region based on second input image data in the data of the projection target image, which corresponds to the second superimposed region, and the first brightness.

CROSS REFERENCE TO RELATED APPLICATION

This is a continuation of International Application No.PCT/JP2020/004666 filed on Feb. 6, 2020, and claims priority fromJapanese Patent Application No. 2019-061683 filed on Mar. 27, 2019, theentire disclosures of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to an image processing device, aprojection system, an image processing method, and a computer readablemedium storing an image processing program.

2. Description of the Related Art

A method is known in which one image is divided to generate a pluralityof division images, and a plurality of projectors projects the divisionimages, respectively, to display one image on a large screen (forexample, see JP2005-286772A and JP2014-194464A).

SUMMARY OF THE INVENTION

In a case in which the plurality of division images are projected anddisplayed on the large screen, the adjacent division images partiallyoverlap each other. For example, in a case in which a predeterminedimage is displayed on the large screen, it is conceivable that aspecific image (for example, a black image or a gray image) havingsufficiently low brightness is displayed in a superimposed region of onedivision image and the other division image, and the predetermined imageis displayed as it is in the other division image.

However, in a projector of a type that controls gradation of aprojection image by controlling a transmission amount of light from alight source, even in a state in which the specific image is displayed,a minute amount of light from the light source is incident on aprojection surface, and the projected specific image itself has slightbrightness. Therefore, in a composite projection image obtained byoverlapping two division images, the gradation of an overlapping regionand the gradation of other regions are deviated, and a quality of thecomposite projection image deteriorates depending on a content of theimage. In JP2005-286772A and JP2014-194464A, it is not assumed that thecomposite projection image is displayed with the overlapping region inone of the two division images as the specific image.

The present invention has been made in view of the above circumstances,and is to provide an image processing device for a projection system, aprojection system, an image processing method, and a computer-readablemedium storing an image processing program which can improve an imagequality by aligning gradation of a projection image in a case in which apart of a plurality of images is overlapped and projected.

An image processing device according to an aspect of the presentinvention is an image processing device for a projection system thatdisplays a projection target image by projecting a first image in afirst projection range from a first projection unit and projecting asecond image in a second projection range that overlaps a part of thefirst projection range from a second projection unit, in which a regionof the first image, which is projected on an overlapping portion of thefirst projection range and the second projection range, is defined as afirst superimposed region and a region of the first image other than thefirst superimposed region is defined as a first non-superimposed region,a region of the second image, which is projected on the overlappingportion, is defined as a second superimposed region and a region of thesecond image other than the second superimposed region is defined as asecond non-superimposed region, the image processing device comprises animage generation unit that generates first data for display of the firstimage and second data for display of the second image from data of theprojection target image, and a brightness acquisition unit that acquiresfirst brightness which is brightness of the overlapping portion in astate in which a specific image is projected on the overlapping portiononly from the first projection unit and second brightness which isbrightness of the overlapping portion in a state in which the specificimage is projected on the overlapping portion only from the secondprojection unit, and the image generation unit generates data forprojecting the specific image, as a first portion in the first data fordisplay, which corresponds to the first superimposed region, generates asecond portion in the first data for display, which corresponds to thefirst non-superimposed region, based on first input image data in thedata of the projection target image, which corresponds to the firstnon-superimposed region, and the second brightness, and generates athird portion in the second data for display, which corresponds to thesecond superimposed region, based on second input image data in the dataof the projection target image, which corresponds to the secondsuperimposed region, and the first brightness.

A projection system according to another aspect of the present inventioncomprises the image processing device, the first projection unit, andthe second projection unit.

An image processing method according to still another aspect of thepresent invention is an image processing method in which, for displayinga projection target image by projecting a first image in a firstprojection range from a first projection unit and projecting a secondimage in a second projection range that overlaps a part of the firstprojection range from a second projection unit, first data for displayof the first image and second data for display of the second image aregenerated from data of the projection target image, in which a region ofthe first image, which is projected on an overlapping portion of thefirst projection range and the second projection range, is defined as afirst superimposed region and a region of the first image other than thefirst superimposed region is defined as a first non-superimposed region,a region of the second image, which is projected on the overlappingportion, is defined as a second superimposed region and a region of thesecond image other than the second superimposed region is defined as asecond non-superimposed region, and the image processing methodcomprises a brightness acquisition step of acquiring first brightnesswhich is brightness of the overlapping portion in a state in which aspecific image is projected on the overlapping portion only from thefirst projection unit and second brightness which is brightness of theoverlapping portion in a state in which the specific image is projectedon the overlapping portion only from the second projection unit, and animage generation step of generating data for projecting the specificimage, as a first portion in the first data for display, whichcorresponds to the first superimposed region, generating a secondportion in the first data for display, which corresponds to the firstnon-superimposed region based on first input image data in the data ofthe projection target image, which corresponds to the firstnon-superimposed region, and the second brightness, and generating athird portion in the second data for display, which corresponds to thesecond superimposed region based on second input image data in the dataof the projection target image, which corresponds to the secondsuperimposed region, and the first brightness.

An image processing program stored in a non-transitory computer readablemedium according to still another aspect of the present invention is animage processing program causing a computer to perform an imageprocessing method in which, for displaying a projection target image byprojecting a first image in a first projection range from a firstprojection unit and projecting a second image in a second projectionrange that overlaps a part of the first projection range from a secondprojection unit, the first image and the second image are generated fromthe projection target image, in which in the image processing method, aregion of the first image, which is projected on an overlapping portionof the first projection range and the second projection range, isdefined as a first superimposed region and a region of the first imageother than the first superimposed region is defined as a firstnon-superimposed region, a region of the second image, which isprojected on the overlapping portion, is defined as a secondsuperimposed region and a region of the second image other than thesecond superimposed region is defined as a second non-superimposedregion, and the image processing method comprises a brightnessacquisition step of acquiring first brightness which is brightness ofthe overlapping portion in a state in which a specific image isprojected on the overlapping portion only from the first projection unitand second brightness which is brightness of the overlapping portion ina state in which the specific image is projected on the overlappingportion only from the second projection unit, and an image generationstep of generating a black image as the first superimposed region,generating the first non-superimposed region based on a first inputimage of the projection target image, which corresponds to the firstnon-superimposed region, and the second brightness, and generating thesecond superimposed region based on a second input image of theprojection target image, which corresponds to the second superimposedregion, and the first brightness.

According to the present invention, it is possible to provide an imageprocessing device for a projection system, a projection system, an imageprocessing method, and an image processing program which can improve animage quality by aligning gradation of a projection image as a whole ina case in which a part of a plurality of images is overlapped andprojected.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing a schematic configuration of aprojection system 100, which is an embodiment of a projection system ofthe present invention.

FIG. 2 is a schematic diagram showing an internal configuration of afirst projection device 1 shown in FIG. 1.

FIG. 3 is a diagram schematically showing an image projected on a firstprojection range 10 from the first projection device 1 when a projectiontarget image is displayed.

FIG. 4 is a diagram schematically showing an image projected on a secondprojection range 20 from a second projection device 2 when a projectiontarget image is displayed.

FIG. 5 is a functional block diagram of a control device 4 shown in FIG.1.

FIG. 6 is a flowchart for describing a measurement operation of firstbrightness in an adjustment mode.

FIG. 7 is a schematic diagram showing an image projected on a screen 6when the first brightness is measured.

FIG. 8 is a flowchart for describing a measurement operation of secondbrightness in the adjustment mode.

FIG. 9 is a schematic diagram showing an image projected on the screen 6when the second brightness is measured.

FIG. 10 is a flowchart for describing an operation of the control device4 when the projection target image is displayed.

FIG. 11 is a flowchart for describing the details of first imageprocessing in step S22 of FIG. 10.

FIG. 12 is a flowchart for describing the details of second imageprocessing in step S25 of FIG. 10.

FIG. 13 is a flowchart for describing a modification example of theoperation of the control device 4 when the projection target image isdisplayed.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described withreference to the drawings.

FIG. 1 is a schematic diagram showing a schematic configuration of aprojection system 100, which is the embodiment of a projection system ofthe present invention. The projection system 100 comprises a firstprojection device 1, a second projection device 2, a control device 4,an imaging unit 5, and a screen 6. Each of the first projection device 1and the second projection device 2 is a projector of a type thatcontrols gradation of a projection image by controlling a transmissionamount of light from a light source, and includes, for example, a liquidcrystal projector or a projector using a liquid crystal on silicon(LCOS). Hereinafter, it is assumed that each of the first projectiondevice 1 and the second projection device 2 is the liquid crystalprojector.

The projection system 100 displays a horizontally long projection targetimage by projecting a division image on a first projection range 10 ofthe screen 6 from the first projection device 1, projecting the divisionimage, from the second projection device 2, on a second projection range20 of the screen 6 which overlaps a part of the first projection range10, and joining these two division images.

The control device 4 is a device including a control unit includingvarious processors, a communication interface (not shown) whichcommunicates with each unit, and a storage medium 4 a such as a harddisk, a solid state drive (SSD), or a read only memory (ROM), andcontrols the first projection device 1, the second projection device 2,and the imaging unit 5 in an integrated manner.

Examples of the various processors of the control unit of the controldevice 4 include a central processing unit (CPU), which is ageneral-purpose processor that executes a program and performs variousprocessing, programmable logic device (PLD), which is a processor whosecircuit configuration can be changed after manufacturing, such as fieldprogrammable gate array (FPGA), or a dedicated electric circuit, whichis a processor having a circuit configuration specially designed forexecuting specific processing such as an application specific integratedcircuit (ASIC), and the like. The structure of these various processorsis, more specifically, an electric circuit in which circuit elementssuch as semiconductor elements are combined. The control unit of thecontrol device 4 may be configured by one of the various processors, ormay be configured by a combination of two or more processors of the sametype or different types (for example, a combination of a plurality ofthe FPGAs or a combination of the CPU and the FPGA).

The imaging unit 5 comprises an imaging element such as a chargedcoupled device (CCD) type image sensor or a metal oxide semiconductor(MOS) type image sensor which images a subject through an imagingoptical system, and images at least a range obtained by combining thefirst projection range 10 and the second projection range 20 on thescreen 6. The captured image captured by the imaging unit 5 is input tothe control device 4.

FIG. 2 is a schematic diagram showing an internal configuration of thefirst projection device 1 shown in FIG. 1. Note that an internalconfiguration of the second projection device 2 shown in FIG. 1 is thesame as that of the first projection device 1, and thus the descriptionthereof will be omitted. The first projection device 1 comprises aprojection unit 13 and a control unit 14.

The projection unit 13 comprises a display unit 11 including a lightsource 11 a and an optical modulation unit 11 b, and a projectionoptical system 12.

The light source 11 a includes a light emitting element such as a laseror a light emitting diode (LED), and emits white light, for example.

The optical modulation unit 11 b includes three liquid crystal panelswhich modulate, based on image information, each color light emittedfrom the light source 11 a and separated into three colors of red, blue,and green by a color separation mechanism (not shown) to emit each colorimage. These three liquid crystal panels may be equipped with red, blue,and green filters, respectively, and modulate the white light emittedfrom the light source 11 a by each liquid crystal panel to emit eachcolor image.

The projection optical system 12 receives light from the display unit11, and includes, for example, a relay optical system including at leastone lens. The light passing through the projection optical system 12 isprojected on the screen 6.

The control unit 14 controls the projection unit 13 based on data fordisplay input from the control device 4 to project an image based on thedata for display on the screen 6. The data for display input to thecontrol unit 14 includes three of data for red display, data for bluedisplay, and data for green display.

In each of the first projection device 1 and the second projectiondevice 2, brightness of the light emitted from the light source 11 a canbe set ink stages (k is a natural number of 2 or more). The brightnessof the projection target image projected on the screen 6 can be adjustedby changing the brightness setting.

FIG. 3 is a diagram schematically showing the image projected on thefirst projection range 10 from the first projection device 1 when theprojection target image is displayed. When the projection target imageis displayed, as shown in FIG. 3, a first division image 10G isprojected on the first projection range 10. The first division image 10Gincludes a first non-superimposed region 10 b and a first superimposedregion 10 a. First data for display used for projecting the firstdivision image 10G is generated by the control device 4 and input to thecontrol unit 14 of the first projection device 1.

The first superimposed region 10 a is a region projected on anoverlapping portion 10A of the first projection range 10 with the secondprojection range 20. The first superimposed region 10 a of the firstdivision image 10G is generated based on a first portion in the firstdata for display, which corresponds to the first superimposed region 10a, input to the control unit 14 of the first projection device 1. Thefirst portion of the first data for display is data in which brightnessvalues of all pixels in each color (red, blue, and green) are set to theminimum value (specifically, “0”) (hereinafter referred to as blackimage data). Here, even in a case in which the first portion is theblack image data, a lower limit value of a light transmission amount ofeach pixel in the optical modulation unit 11 b is not “0”, so that thefirst superimposed region 10 a is an image region having slightbrightness. Hereinafter, the image projected on the screen 6 based onthe black image data is referred to as a black image.

The first non-superimposed region 10 b is a region projected on anon-overlapping portion 10B of the first projection range 10 with thesecond projection range 20. The first non-superimposed region 10 b isgenerated based on a second portion in the first data for display, whichcorresponds to the first non-superimposed region 10 b. In the secondportion of the first data for display, the brightness value of eachpixel in each color is a value determined based on the data of theprojection target image input to the control device 4.

FIG. 4 is a diagram schematically showing an image projected on thesecond projection range 20 from the second projection device 2 when theprojection target image is displayed. When the projection target imageis displayed, as shown in FIG. 4, a second division image 20G isprojected on the second projection range 20. The second division image20G includes a second superimposed region 20 a and a secondnon-superimposed region 20 b. Second data for display used forprojecting the second division image 20G is generated by the controldevice 4 and input to the control unit 14 of the second projectiondevice 2.

The second superimposed region 20 a is a region projected on anoverlapping portion 20A of the second projection range 20 with the firstprojection range 10. The second superimposed region 20 a is generatedbased on a third portion in the second data for display, whichcorresponds to the second superimposed region 20 a. In the third portionof the second data for display, the brightness value of each pixel ineach color is a value determined based on the data of the projectiontarget image input to the control device 4.

The second non-superimposed region 20 b is a region projected on anon-overlapping portion 20B of the second projection range 20 with thefirst projection range 10. The second non-superimposed region 20 b isgenerated based on a fourth portion in the second data for display,which corresponds to the second non-superimposed region 20 b. In thefourth portion of the second data for display, the brightness value ofeach pixel in each color is a value determined based on the data of theprojection target image input to the control device 4.

As shown in FIGS. 3 and 4, in a case in which the projection targetimage is displayed, in the overlapping portion 10A of the firstprojection range 10 (synonymous with the overlapping portion 20A of thesecond projection range 20), the black image (first superimposed region10 a) having slight brightness and the image (second superimposed region20 a) based on the data of the projection target image are displayed inan overlapping manner. Therefore, in the displayed projection targetimage, there is a difference between the minimum brightness of the imagein the overlapping portion 10A (20A) and the minimum brightness of theimage in other portions. The control device 4 performs image processingof correcting the difference in the minimum brightness.

FIG. 5 is a functional block diagram of the control device 4 shown inFIG. 1. The control unit of the control device 4 executes a programincluding an image processing program to function as an image processingdevice including an image generation unit 41, a brightness acquisitionunit 42, a projection control unit 43, and a brightness detection unit44.

The image generation unit 41 generates the first data for display usedfor projecting the first division image 10G from the first projectiondevice 1 and second data for display used for projecting the seconddivision image 20G from the second projection device 2, from the data(hereinafter, also referred to as input image data) of the projectiontarget image input from an external device such as a personal computeror the like.

The brightness acquisition unit 42 acquires, from the storage medium 4a, first brightness (brightness BL1(n) described below), which is thebrightness of the overlapping portion 10A (20A) in a state in which theblack image is projected on the overlapping portion 10A (20A) only fromthe first projection device 1, and second brightness (brightness BL2(n)described below), which is the brightness of the overlapping portion 10A(20A) in the state in which the black image is projected on theoverlapping portion 10A (20A) only from the second projection device 2.

In the projection system 100, an adjustment mode is provided in whichthe first brightness and the second brightness are measured in a statein which the black image is projected on the screen 6 and stored in thestorage medium 4 a. The brightness acquisition unit 42 acquires, by theadjustment mode, the first brightness and the second brightness storedin the storage medium 4 a from the storage medium 4 a. The projectioncontrol unit 43 and the brightness detection unit 44 are blocks thatfunction in the adjustment mode. Hereinafter, an operation in theadjustment mode will be described.

FIG. 6 is a flowchart for describing a measurement operation of thefirst brightness in the adjustment mode. FIG. 7 is a schematic diagramshowing the image projected on the screen 6 when the first brightness ismeasured.

The projection control unit 43 sets a brightness set value n of thelight source 11 a of the first projection device 1 to, for example, theminimum value “1” of the k stages (step S1).

Next, the brightness detection unit 44 projects, for example, an imageof a rectangular frame on the screen 6 from the first projection device1, acquires the captured image obtained by imaging the screen 6 by theimaging unit 5 in that state, detects a position of the rectangularframe from the captured image, recognizes the first projection range 10on the screen 6, and detects the overlapping portion 10A in the firstprojection range 10 (step S2).

The overlapping portion 10A in the first projection range 10 can bedetected based on information on a distance between the first projectiondevice 1 and the second projection device 2, information of an angleformed by a direction of an optical axis of the first projection device1 and a direction of an optical axis of the second projection device 2,and the like. These pieces of information may be manually input to thecontrol device 4, or may be automatically determined by the controldevice 4 by sensors and the like provided in the first projection device1 and the second projection device 2.

Next, the projection control unit 43 projects the black image on thescreen 6 from the first projection device 1, and controls the secondprojection device 2 to be in a non-image projection state (step S3). Bythe process of step S3, as shown in FIG. 7, a black image 15 based onthe black image data is projected on the first projection range 10 ofthe screen 6. As described above, the black image 15 is an image havingslight brightness due to a characteristic of the optical modulation unit11 b of the first projection device 1.

Next, the brightness detection unit 44 acquires the captured imageobtained by imaging the screen 6 by the imaging unit 5 in a state shownin FIG. 7, acquires an image M1 of the overlapping portion 10A in thecaptured image, and calculates brightness (for example, an average valueof the brightness values of all the pixels or a median value of thebrightness values of all the pixels) of the image M1 (step S4).

Next, the brightness detection unit 44 uses the brightness of the imageM1 calculated in step S4 as the brightness BL1(n) of the overlappingportion 10A in a state in which the black image is projected on theoverlapping portion 10A of the first projection range 10 and stores thecalculated brightness in the storage medium 4 a (step S5). A value of“n” in step S5 is the value set in step S1. The brightness BL1(n) is theabove-described first brightness.

Next, in a case in which the brightness set value n is not k (step S6:NO), the projection control unit 43 increases the brightness set value nby one in step S7 and shifts the process to step S3, and in a case inwhich the brightness set value n is k (step S6: YES), the projectioncontrol unit 43 terminates the process. As a result, k pieces of firstbrightness (BL1(1), BL1(2), BL1(k)) are stored in the storage medium 4a.

FIG. 8 is a flowchart for describing a measurement operation of thesecond brightness in the adjustment mode. FIG. 9 is a schematic diagramshowing the image projected on the screen 6 when the second brightnessis measured.

The projection control unit 43 sets a brightness set value n of thelight source 11 a of the second projection device 2 to, for example, theminimum value “1” of the k stages (step S11).

Next, the brightness detection unit 44 projects, for example, an imageof a rectangular frame on the screen 6 from the second projection device2, acquires the captured image obtained by imaging the screen 6 by theimaging unit 5 in that state, detects a position of the rectangularframe from the captured image, recognizes the second projection range 20on the screen 6, and detects the overlapping portion 20A in the secondprojection range 20 (step S12).

The overlapping portion 20A in the second projection range 20 can bedetected based on information on a distance between the first projectiondevice 1 and the second projection device 2, information of an angleformed by a direction of an optical axis of the first projection device1 and a direction of an optical axis of the second projection device 2,and the like. These pieces of information may be manually input to thecontrol device 4, or may be automatically determined by the controldevice 4 by sensors and the like provided in the first projection device1 and the second projection device 2.

Next, the projection control unit 43 projects the black image on thescreen 6 from the second projection device 2, and controls the firstprojection device 1 to be in a non-image projection state (step S13). Bythe process of step S13, as shown in FIG. 9, a black image 15 based onthe black image data is projected on the second projection range 20 ofthe screen 6. As described above, the black image 15 is an image havingslight brightness due to a characteristic of the optical modulation unit11 b of the second projection device 2.

Next, the brightness detection unit 44 acquires the captured imageobtained by imaging the screen 6 by the imaging unit 5 in a state shownin FIG. 9, acquires an image M2 of the overlapping portion 20A in thecaptured image, and calculates brightness (for example, the averagevalue of the brightness values of all the pixels or the median value ofthe brightness values of all the pixels) of the image M2 (step S14).

Next, the brightness detection unit 44 uses the brightness of the imageM2 calculated in step S14 as the brightness BL2(n) of the overlappingportion 20A in a state in which the black image is projected on theoverlapping portion 20A of the second projection range 20 and stores thecalculated brightness in the storage medium 4 a (step S15). A value of“n” in step S15 is the value set in step S11. The brightness BL2(n) isthe above-described second brightness.

Next, in a case in which the brightness set value n is not k (step S16:NO), the projection control unit 43 increases the brightness set value nby one in step S17 and shifts the process to step S13, and in a case inwhich the brightness set value n is k (step S16: YES), the projectioncontrol unit 43 terminates the process. As a result, k pieces of secondbrightness (BL2(1), BL2(2), BL2(k)) are stored in the storage medium 4a.

The image generation unit 41 shown in FIG. 5 generates the black imagedata as the first portion (data for projecting the first superimposedregion 10 a) in the first data for display, which corresponds to thefirst superimposed region 10 a, and generates the second portion (datafor projecting the first non-superimposed region 10 b) in the first datafor display, which corresponds to the first non-superimposed region 10b, based on the first input image data in the input image data, whichcorresponds to the first non-superimposed region 10 b, and thebrightness BL2(n).

Further, the image generation unit 41 generates the third portion (datafor projecting the second superimposed region 20 a) in the second datafor display, which corresponds to the second superimposed region 20 a,based on the second input image data in the input image data, whichcorresponds to the second superimposed region 20 a, and the brightnessBL1(n).

Further, the image generation unit 41 generates the fourth portion (datafor projecting the second non-superimposed region 20 b) in the seconddata for display, which corresponds to the second non-superimposedregion 20 b, based on the third input image data in the input imagedata, which corresponds to the second non-superimposed region 20 b, andthe brightness BL1(n).

FIG. 10 is a flowchart for describing an operation of the control device4 when the projection target image is displayed. FIG. 11 is a flowchartfor describing the details of first image processing in step S22 of FIG.10. FIG. 12 is a flowchart for describing the details of second imageprocessing in step S25 of FIG. 10. Here, the operation when theprojection target image is displayed in the state in which thebrightness set values n of the first projection device 1 and the secondprojection device 2 are set to m (m is any one of 1 to k) will bedescribed.

In a case in which the input image data is acquired, the imagegeneration unit 41 divides the input image data into first image datafor projecting the input image data in the first projection range 10 andsecond image data for projecting in the second projection range 20 (stepS20). Specifically, the image generation unit 41 trims a portion of theinput image data, which corresponds to the first projection range 10, toobtain the first image data, and trims a portion of the input imagedata, which corresponds to the second projection range 20, to obtain thesecond image data.

Next, the brightness acquisition unit 42 acquires, from the storagemedium 4 a, the first brightness (brightness BL1(n=m)) and the secondbrightness (brightness BL2(n=m)), which correspond to the brightness setvalue m (step S21).

Next, the image generation unit 41 performs the first image processingon the portion in the first image data, which corresponds to the firstnon-superimposed region 10 b (first input image data described above)(step S22). Specifically, the image generation unit 41 performs theprocess shown in FIG. 11 with respect to a brightness value p1 of eachpixel of each color (red, blue, and green) image data of the first inputimage data. First, the image generation unit 41 compares a value{γ×BL2(n=m)}, which is obtained by multiplying the brightness BL2(n=m)acquired in step S21 by a coefficient γ, with the brightness value p1 ofa processing target. The coefficient γ is a coefficient for correctingthe brightness value of each pixel of the data for display of any imagesuch that the brightness of the image projected on the screen 6 is thebrightness BL2(n).

In a case in which the brightness value p1 of the processing target isequal to or more than {γ×BL2(n=m)} (step S31: YES), the image generationunit 41 sets the brightness value p1 of the processing target as it is,as the brightness value P1 after the first image processing (step S32).

In a case in which the brightness value p1 of the processing target isless than {γ×BL2(n=m)} (step S31: NO), the image generation unit 41 sets{γ×BL2(n=m)}, as the brightness value P1 after third image processing(step S33).

Next, the image generation unit 41 substitutes the portion in the firstimage data, which corresponds to the first superimposed region 10 a,with the black image data (step S23).

Next, the image generation unit 41 performs the second image processingon the portion in the second image data, which corresponds to the secondsuperimposed region 20 a (second input image data described above) (stepS24). Specifically, the image generation unit 41 generates eachbrightness value P1 after the processing by subtracting, from thebrightness value p1 of each pixel of each color (red, blue, and green)image data of the second input image data, a value {γ×BL1(n=m)} obtainedby multiplying the brightness BL1(n=m) acquired in step S21 by thecoefficient γ.

Next, the image generation unit 41 performs the third image processingon the portion in the second image data, which corresponds to the secondnon-superimposed region 20 b (third input image data described above)(step S25). Specifically, the image generation unit 41 performs theprocess shown in FIG. 12 with respect to the brightness value p1 of eachpixel of each color (red, blue, and green) image data of the secondinput image data. First, the image generation unit 41 compares a value{γ×BL1(n=m)}, which is obtained by multiplying the brightness BL1(n=m)acquired in step S21 by the coefficient γ, with the brightness value p1of the processing target.

In a case in which the brightness value p1 of the processing target isequal to or more than {γ×BL1(n=m)} (step S41: YES), the image generationunit 41 sets the brightness value p1 of the processing target as it is,as the brightness value P1 after the third image processing (step S42).

In a case in which the brightness value p1 of the processing target isless than {γ×BL1(n=m)} (step S41: NO), the image generation unit 41 sets{γ×BL1(n=m)}, as the brightness value P1 after the third imageprocessing (step S43).

Then, the image generation unit 41 outputs, as the first data fordisplay, the first image data after the image processing obtained in theprocesses of steps S22 and S23 to the control unit 14 of the firstprojection device 1 (step S26) and outputs, as the second data fordisplay, the second image data after image processing obtained in theprocesses of steps S24 and S25 to the control unit 14 of the secondprojection device 2 (step S27).

As described above, with the projection system 100, the brightness valueof each pixel is uniformly reduced by {γ×BL1(n)} for the portion in thesecond data for display, which corresponds to the second superimposedregion 20 a. That is, in a case of the brightness set value n=m, thebrightness of the image projected on the overlapping portion 10A basedon this portion is reduced by BL1(n=m).

Further, the portion in the first data for display, which corresponds tothe first superimposed region 10 a, is the black image data. Therefore,in a case of the brightness set value n=m, the brightness of the blackimage projected on the overlapping portion 10A based on the black imagedata is BL1(n=m). That is, the overlapping portion 10A is in a state inwhich the image of which the brightness is reduced by BL1(n=m) and theimage of which the brightness is BL1(n=m) are superimposed and thesepieces of the brightness are offset, and the minimum value of thebrightness of the image projected on the overlapping portion 10A is thebrightness BL2(n=m).

On the other hand, for the portion in the first data for display, whichcorresponds to the first non-superimposed region 10 b, the brightnessvalue of the pixel having the brightness value less than {γ×BL2(n)} isincreased to {γ×BL2(n)}. Further, for the portion in the second data fordisplay, which corresponds to the second non-superimposed region 20 b,the brightness value of the pixel having the brightness value less than{γ×BL1(n)} is increased to {γ×BL1(n)}. That is, a lower limit value ofthe brightness of the image projected on the non-overlapping portion 10Bin a case of the brightness set value n=m is BL2(n=m), and the lowerlimit value of the brightness of the image projected on thenon-overlapping portion 20B in a case of the brightness set value n=m isBL1(n=m). BL1(n) and BL2(n) are the same except for individualdifferences in the devices or environmental conditions. That is, adifference between BL1(n) and BL2(n) is negligibly small.

Therefore, with the projection system 100, the minimum brightness of theimage projected on the non-overlapping portion 10B, the minimumbrightness of the image projected on the overlapping portion 10A, andthe minimum brightness of the image projected on the non-overlappingportion 20B can be set to substantially the same value, and it ispossible to obtain a state in which the gradation of the displayedprojection target image is aligned as a whole.

Since such an effect can be obtained by simple processing such as thefirst image processing, the second image processing, and the third imageprocessing, which are described above, it is possible to improve theprojection image quality while reducing the system construction cost.

Further, with the projection system 100, since the adjustment mode isprovided, even in a case in which various situations occur, such as achange in installation locations of the first projection device 1 andthe second projection device 2, a change in a reflection characteristicof the screen 6, and a change in each model of the first projectiondevice 1 and the second projection device 2, the first brightness andthe second brightness in that situation can be acquired, and the qualityof the projection target image can be improved.

Further, with the projection system 100, the first brightness and thesecond brightness for each brightness set value n are stored in thestorage medium 4 a, and the first image processing, the second imageprocessing, and the third image processing are performed based on thefirst brightness and the second brightness which correspond to thebrightness set value when the projection target image is displayed.Therefore, the projection image quality can be improved by aligning thegradation regardless of the brightness setting at the time of imageprojection.

Note that in the above description, it has been described that theprojection system 100 has the adjustment mode, but the adjustment modeis not essential. For example, when the control device 4 ismanufactured, the first brightness and the second brightness may bemeasured by the methods shown in FIGS. 6 to 9 in a factory or the like,the measured first brightness and second brightness may be stored in thestorage medium 4 a, and then the control device 4 may be shipped. Withthis configuration, the projection image quality can be sufficientlyimproved as long as the projection system 100 is assumed to be used onlyin a specific place. Further, the manufacturing cost of the controldevice 4 can be reduced.

FIG. 13 is a flowchart for describing a modification example of theoperation of the control device 4 when the projection target image isdisplayed. The flowchart shown in FIG. 13 is the same as that of FIG. 10except that steps S51 to S54 are added. In FIG. 13, the same process asin FIG. 10 is designated by the same reference numeral and thedescription thereof will be omitted.

After step S21, the image generation unit 41 determines whether or noteach of the brightness BL1(n=m) and the brightness BL2(n=m) is equal toor less than a threshold value (step S51). In a case in which any one ofthe brightness BL1(n=m) or the brightness BL2(n=m) exceeds the thresholdvalue (step S51: NO), the image generation unit 41 performs theprocesses after step S22.

In a case in which both the brightness BL1(n=m) and the brightnessBL2(n=m) are equal to or less than the threshold value (step S51: YES),the image generation unit 41 performs the processes after step S52. Instep S52, the image generation unit 41 substitutes the portion in thefirst image data, which corresponds to the first superimposed region 10a with the black image data. Then, the image generation unit 41 outputs,as the first data for display, the first image data after the processingin step S51 to the control unit 14 of the first projection device 1(step S53), and outputs, as the second data for display, the secondimage data generated in step S20 as it is to the control unit 14 of thesecond projection device 2 (step S54).

According to this modification example, in a case in which thebrightness set value of the light source 11 a when the projection targetimage is displayed is low or a case in which the first brightness andthe second brightness are negligibly small due to the reflectioncharacteristic of the screen 6, the use environment of the projectionsystem 100, the performance of each projection device, and the like, theimage processing in steps S22 to S27 is not performed.

In this case, the lower limit value of the brightness of the imageprojected on the non-overlapping portion 10B is the first brightness,the lower limit value of the brightness of the image projected on theoverlapping portion 10A is a total value of the first brightness and thesecond brightness, and the lower limit value of the brightness of theimage projected on the non-overlapping portion 20B is the secondbrightness. However, since the first brightness and the secondbrightness are very small values, the difference in the minimumbrightness in the entire projection target image is inconspicuous.Further, in this case, the gradation of the projection target image canbe improved and the quality of the projection image can be improved ascompared with the case in which the processes after step S22 areperformed.

Up to this point, the projection system 100 has been described to havetwo projection devices, but the control device 4 may be connected tothree or more projection devices to control the projection devices. Evenin this case, the projection target image can be displayed on the largescreen with high image quality.

Further, the first portion in the first data for display need only havethe brightness values of all the pixels in each color (red, blue, andgreen) close to the minimum value and need not be the black image data.For example, the first portion may be gray image data for displaying aso-called gray image in which the brightness values of all the pixelsare slightly higher than the minimum value. In this case, all the blackimages in the adjustment mode described with reference to FIGS. 6 to 9need only be replaced with the gray images. Further, the “black imagedata” in step S23 of FIGS. 10 and 13 and step S52 of FIG. 13 need onlybe replaced with the “gray image data”.

Also, in FIGS. 10 and 13, step S25 may be omitted. Even in this case,since the minimum brightness of the image projected on thenon-overlapping portion 10B and the minimum brightness of the imageprojected on the overlapping portion 10A can be set to substantially thesame value, the image quality of the projection target image can beimproved as compared with the case in which the first image processingand the second image processing are not performed.

Although in the projection system 100, the imaging unit 5 is providedindependently, the imaging unit 5 may be built in the first projectiondevice 1 and the second projection device 2.

At least the following matters are described in the presentspecification. Note that the components and the like corresponding tothe above embodiments are shown in parentheses, but the presentinvention is not limited thereto.

(1) An image processing device (control device 4) for a projectionsystem (projection system 100) that displays a projection target imageby projecting a first image (first division image 10G) in a firstprojection range (first projection range 10) from a first projectionunit (projection unit 13 of first projection device 1) and projecting asecond image (second division image 20G) in a second projection range(second projection range 20) that overlaps a part of the firstprojection range from a second projection unit (projection unit 13 ofsecond projection device 2), in which a region of the first image, whichis projected on an overlapping portion (overlapping portion 10A) of thefirst projection range and the second projection range, is defined as afirst superimposed region (first superimposed region 10 a) and a regionof the first image other than the first superimposed region is definedas a first non-superimposed region (first non-superimposed region 10 b),a region of the second image, which is projected on the overlappingportion, is defined as a second superimposed region (second superimposedregion 20 a) and a region of the second image other than the secondsuperimposed region is defined as a second non-superimposed region(second non-superimposed region 20 b), the image processing devicecomprises an image generation unit (image generation unit 41) thatgenerates first data for display of the first image and second data fordisplay of the second image from data of the projection target image,and a brightness acquisition unit (brightness acquisition unit 42) thatacquires first brightness (brightness BL1(n)) which is brightness of theoverlapping portion in a state in which a specific image (black image15) is projected on the overlapping portion only from the firstprojection unit and second brightness (brightness BL2(n)) which isbrightness of the overlapping portion in a state in which the specificimage is projected on the overlapping portion only from the secondprojection unit, and the image generation unit generates data (blackimage data) for projecting the specific image, as a first portion, whichcorresponds to the first superimposed region, in the first data fordisplay, generates a second portion in the first data for display, whichcorresponds to the first non-superimposed region based on first inputimage data in the data of the projection target image, which correspondsto the first non-superimposed region, and the second brightness, andgenerates a third portion in the second data for display, whichcorresponds to the second superimposed region based on second inputimage data in the data of the projection target image, which correspondsto the second superimposed region, and the first brightness.(2) The image processing device according to (1), in which the imagegeneration unit generates a fourth portion in the second data fordisplay, which corresponds to the second non-superimposed region, basedon third input image data in the data of the projection target image,which corresponds to the second non-superimposed region, and the firstbrightness.(3) The image processing device according to (2), in which the imagegeneration unit generates the second portion by correcting brightness ofa pixel, which is less than the second brightness, among pixels of thefirst input image data to the second brightness, generates the thirdportion by reducing brightness of each pixel of the second input imagedata by the first brightness, and generates the fourth portion bycorrecting brightness of a pixel, which is less than the firstbrightness, among pixels of the third input image data to the firstbrightness.(4) The image processing device according to (2) or (3), in which, in acase in which the first brightness and the second brightness are equalto or less than a threshold value, the image generation unit regards thefirst input image data as the second portion, the second input imagedata as the third portion, and the third input image data as the fourthportion.(5) The image processing device according to any one of (1) to (4),further comprising a projection control unit (projection control unit43) that performs first projection control of projecting the specificimage on the overlapping portion only from the first projection unit andsecond projection control of projecting the specific image on theoverlapping portion only from the second projection unit, and abrightness detection unit (brightness detection unit 44) that detectsthe first brightness of the overlapping portion in a state in which thefirst projection control is performed and stores the detected firstbrightness in a storage medium (storage medium 4 a), and detects thesecond brightness of the overlapping portion in a state in which thesecond projection control is performed and stores the detected secondbrightness in the storage medium (storage medium 4 a), in which thebrightness acquisition unit acquires the first brightness and the secondbrightness from the storage medium.(6) The image processing device according to (5), in which theprojection control unit performs the first projection control aplurality of times by changing a set value (brightness set value n) ofbrightness of a first light source (light source 11 a) included in thefirst projection unit, and performs the second projection control aplurality of times by changing a set value (brightness set value n) ofbrightness of a second light source (light source 11 a) included in thesecond projection unit, the brightness detection unit stores the firstbrightness detected for each first projection control in associationwith the set value of the brightness of the first light source in astate in which the first projection control is performed, and stores thesecond brightness detected for each second projection control inassociation with the set value of the brightness of the second lightsource in a state in which the second projection control is performed,and the brightness acquisition unit acquires, from the storage medium,the first brightness and the second brightness which correspond to theset values of the brightness of the first light source and thebrightness of the second light source set when the projection targetimage is displayed.(7) The image processing device according to any one of (1) to (4), inwhich the brightness acquisition unit acquires, from the firstbrightness and the second brightness stored in association with each setvalue of brightness of a first light source included in the firstprojection unit and a second light source included in the secondprojection unit, the first brightness and the second brightness whichcorrespond to the set values of the brightness of the first light sourceand the brightness of the second light source set when the projectiontarget image is displayed.(8) A projection system comprising the image processing device accordingto any one of (1) to (7), the first projection unit, and the secondprojection unit.(9) An image processing method in which, for displaying a projectiontarget image by projecting a first image in a first projection rangefrom a first projection unit and projecting a second image in a secondprojection range that overlaps a part of the first projection range froma second projection unit, first data for display of the first image andsecond data for display of the second image are generated from data ofthe projection target image, in which a region of the first image, whichis projected on an overlapping portion of the first projection range andthe second projection range, is defined as a first superimposed regionand a region of the first image other than the first superimposed regionis defined as a first non-superimposed region, a region of the secondimage, which is projected on the overlapping portion, is defined as asecond superimposed region and a region of the second image other thanthe second superimposed region is defined as a second non-superimposedregion, and the image processing method comprises a brightnessacquisition step of acquiring first brightness which is brightness ofthe overlapping portion in a state in which a specific image isprojected on the overlapping portion only from the first projection unitand second brightness which is brightness of the overlapping portion ina state in which the specific image is projected on the overlappingportion only from the second projection unit, and an image generationstep of generating data for projecting the specific image, as a firstportion in the first data for display, which corresponds to the firstsuperimposed region, generating a second portion in the first data fordisplay, which corresponds to the first non-superimposed region based onfirst input image data in the data of the projection target image, whichcorresponds to the first non-superimposed region, and the secondbrightness, and generating a third portion in the second data fordisplay, which corresponds to the second superimposed region based onsecond input image data in the data of the projection target image,which corresponds to the second superimposed region, and the firstbrightness.(10) The image processing method according to (9), in which in the imagegeneration step, a fourth portion in the second data for display, whichcorresponds to the second non-superimposed region, is further generatedbased on third input image data in the data of the projection targetimage, which corresponds to the second non-superimposed region, and thefirst brightness.(11) The image processing method according to (10), in which in theimage generation step, the second portion is generated by correctingbrightness of a pixel, which is less than the second brightness, amongpixels of the first input image data to the second brightness, the thirdportion is generated by reducing brightness of each pixel of the secondinput image data by the first brightness, and the fourth portion isgenerated by correcting brightness of a pixel, which is less than thefirst brightness, among pixels of the third input image data to thefirst brightness.(12) The image processing method according to (10) or (11), in which inthe image generation step, in a case in which the first brightness andthe second brightness are equal to or less than a threshold value, thefirst input image data is regarded as the second portion, the secondinput image data is regarded as the third portion, and the third inputimage data is regarded as the fourth portion.(13) The image processing method according to any one of (9) to (12),further comprising a projection control step of performing firstprojection control of projecting the specific image on the overlappingportion only from the first projection unit and second projectioncontrol of projecting the specific image on the overlapping portion onlyfrom the second projection unit, and a brightness detection step ofdetecting the first brightness of the overlapping portion in a state inwhich the first projection control is performed and storing the detectedfirst brightness in a storage medium, and detecting the secondbrightness of the overlapping portion in a state in which the secondprojection control is performed and storing the detected secondbrightness in the storage medium, in which in the brightness acquisitionstep, the first brightness and the second brightness are acquired fromthe storage medium.(14) The image processing method according to (13), in which in theprojection control step, the first projection control is performed aplurality of times by changing a set value of brightness of a firstlight source included in the first projection unit, and the secondprojection control is performed a plurality of times by changing a setvalue of brightness of a second light source included in the secondprojection unit, in the brightness detection step, the first brightnessdetected for each of the first projection controls is stored inassociation with the set value of the brightness of the first lightsource in a state in which the first projection control is performed,and the second brightness detected for each of the second projectioncontrols is stored in association with the set value of the brightnessof the second light source in a state in which the second projectioncontrol is performed, and in the brightness acquisition step, from thestorage medium, the first brightness and the second brightness whichcorrespond to the set values of the brightness of the first light sourceand the brightness of the second light source set when the projectiontarget image is displayed are acquired.(15) The image processing method according to any one of (9) to (12), inwhich in the brightness acquisition step, from the first brightness andthe second brightness stored in association with each set value ofbrightness of a first light source included in the first projection unitand a second light source included in the second projection unit, thefirst brightness and the second brightness which correspond to the setvalues of the brightness of the first light source and the brightness ofthe second light source set when the projection target image isdisplayed are acquired.(16) An image processing program causing a computer to perform an imageprocessing method in which, for displaying a projection target image byprojecting a first image in a first projection range from a firstprojection unit and projecting a second image in a second projectionrange that overlaps a part of the first projection range from a secondprojection unit, the first image and the second image are generated fromthe projection target image, in which in the image processing method, aregion of the first image, which is projected on an overlapping portionof the first projection range and the second projection range, isdefined as a first superimposed region and a region of the first imageother than the first superimposed region is defined as a firstnon-superimposed region, a region of the second image, which isprojected on the overlapping portion, is defined as a secondsuperimposed region and a region of the second image other than thesecond superimposed region is defined as a second non-superimposedregion, and the image processing method comprises a brightnessacquisition step of acquiring first brightness which is brightness ofthe overlapping portion in a state in which a specific image isprojected on the overlapping portion only from the first projection unitand second brightness which is brightness of the overlapping portion ina state in which the specific image is projected on the overlappingportion only from the second projection unit, and an image generationstep of generating a black image as the first superimposed region,generating the first non-superimposed region based on a first inputimage of the projection target image, which corresponds to the firstnon-superimposed region, and the second brightness, and generating thesecond superimposed region based on a second input image of theprojection target image, which corresponds to the second superimposedregion, and the first brightness.

Various embodiments have been described above with reference to thedrawings, but it is needless to say that the present invention is notlimited thereto. It is obvious that those skilled in the art canconceive various changes or modifications within the scope described inthe claims, and naturally, such changes or modifications also belong tothe technical scope of the present invention. Further, the components inthe embodiments described above may be optionally combined withoutdeparting from the spirit of the invention.

Note that the present application is based on a Japanese patentapplication filed on Mar. 27, 2019 (JP2019-061683), the contents ofwhich are incorporated herein by reference.

According to the present invention, in a case in which a part of theplurality of images is overlapped and projected, the gradation of theprojection image can be aligned as a whole to improve the image quality,which is effective for displaying the image on a large screen.

EXPLANATION OF REFERENCES

-   100: projection system-   1: first projection device-   11: display unit-   11 a: light source-   11 b: optical modulation unit-   12: projection optical system-   13: projection unit-   14: control unit-   15: black image-   2: second projection device-   4: control device-   4 a: storage medium-   41: image generation unit-   42: brightness acquisition unit-   43: projection control unit-   44: brightness detection unit-   5: imaging unit-   6: screen-   10: first projection range-   10G: first division image-   10 a: first superimposed region-   10 b: first non-superimposed region-   10A: overlapping portion-   10B: non-overlapping portion-   20: second projection range-   20G: second division image-   20 a: second superimposed region-   20 b: second non-superimposed region-   20A: overlapping portion-   20B: non-overlapping portion

What is claimed is:
 1. An image processing device for a projectionsystem that displays a projection target image by projecting a firstimage in a first projection range from a first projection unit andprojecting a second image in a second projection range, that overlaps apart of the first projection range, from a second projection unit,wherein a region of the first image, which is projected on anoverlapping portion of the first projection range and the secondprojection range, is defined as a first superimposed region and a regionof the first image other than the first superimposed region is definedas a first non-superimposed region, a region of the second image, whichis projected on the overlapping portion, is defined as a secondsuperimposed region and a region of the second image other than thesecond superimposed region is defined as a second non-superimposedregion, the image processing device comprises an image generation unitthat generates first data for display of the first image and second datafor display of the second image from data of the projection targetimage, and a brightness acquisition unit that acquires first brightnesswhich is brightness of the overlapping portion in a state in which aspecific image is projected on the overlapping portion only from thefirst projection unit and second brightness which is brightness of theoverlapping portion in a state in which the specific image is projectedon the overlapping portion only from the second projection unit, and theimage generation unit generates data for projecting the specific image,as a first portion in the first data for display, which corresponds tothe first superimposed region, generates a second portion in the firstdata for display, which corresponds to the first non-superimposed regionbased on first input image data in the data of the projection targetimage, which corresponds to the first non-superimposed region, and thesecond brightness, and generates a third portion in the second data fordisplay, which corresponds to the second superimposed region based onsecond input image data in the data of the projection target image,which corresponds to the second superimposed region, and the firstbrightness.
 2. The image processing device according to claim 1, whereinthe image generation unit generates a fourth portion in the second datafor display, which corresponds to the second non-superimposed region,based on third input image data in the data of the projection targetimage, which corresponds to the second non-superimposed region, and thefirst brightness.
 3. The image processing device according to claim 2,wherein the image generation unit generates the second portion bycorrecting brightness of a pixel, which is less than the secondbrightness, among pixels of the first input image data to the secondbrightness, generates the third portion by reducing brightness of eachpixel of the second input image data by the first brightness, andgenerates the fourth portion by correcting brightness of a pixel, whichis less than the first brightness, among pixels of the third input imagedata to the first brightness.
 4. The image processing device accordingto claim 2, wherein, in a case in which the first brightness and thesecond brightness are equal to or less than a threshold value, the imagegeneration unit regards the first input image data as the secondportion, the second input image data as the third portion, and the thirdinput image data as the fourth portion.
 5. The image processing deviceaccording to claim 3, wherein, in a case in which the first brightnessand the second brightness are equal to or less than a threshold value,the image generation unit regards the first input image data as thesecond portion, the second input image data as the third portion, andthe third input image data as the fourth portion.
 6. The imageprocessing device according to claim 1, further comprising: a projectioncontrol unit that performs first projection control of projecting thespecific image on the overlapping portion only from the first projectionunit and second projection control of projecting the specific image onthe overlapping portion only from the second projection unit; and abrightness detection unit that detects the first brightness of theoverlapping portion in a state in which the first projection control isperformed and stores the detected first brightness in a storage medium,and detects the second brightness of the overlapping portion in a statein which the second projection control is performed and stores thedetected second brightness in the storage medium, wherein the brightnessacquisition unit acquires the first brightness and the second brightnessfrom the storage medium.
 7. The image processing device according toclaim 2, further comprising: a projection control unit that performsfirst projection control of projecting the specific image on theoverlapping portion only from the first projection unit and secondprojection control of projecting the specific image on the overlappingportion only from the second projection unit; and a brightness detectionunit that detects the first brightness of the overlapping portion in astate in which the first projection control is performed and stores thedetected first brightness in a storage medium, and detects the secondbrightness of the overlapping portion in a state in which the secondprojection control is performed and stores the detected secondbrightness in the storage medium, wherein the brightness acquisitionunit acquires the first brightness and the second brightness from thestorage medium.
 8. The image processing device according to claim 6,wherein the projection control unit performs the first projectioncontrol a plurality of times by changing a set value of brightness of afirst light source included in the first projection unit, and performsthe second projection control a plurality of times by changing a setvalue of brightness of a second light source included in the secondprojection unit, the brightness detection unit stores the firstbrightness detected for each of the first projection controls inassociation with the set value of the brightness of the first lightsource in a state in which the first projection control is performed,and stores the second brightness detected for each of the secondprojection controls in association with the set value of the brightnessof the second light source in a state in which the second projectioncontrol is performed, and the brightness acquisition unit acquires, fromthe storage medium, the first brightness and the second brightness whichcorrespond to the set values of the brightness of the first light sourceand the brightness of the second light source set when the projectiontarget image is displayed.
 9. The image processing device according toclaim 1, wherein the brightness acquisition unit acquires, from thefirst brightness and the second brightness stored in association witheach set value of brightness of a first light source included in thefirst projection unit and a second light source included in the secondprojection unit, the first brightness and the second brightness whichcorrespond to the set values of the brightness of the first light sourceand the brightness of the second light source set when the projectiontarget image is displayed.
 10. A projection system comprising: the imageprocessing device according to claim 1; the first projection unit; andthe second projection unit.
 11. An image processing method in which, fordisplaying a projection target image by projecting a first image in afirst projection range from a first projection unit and projecting asecond image in a second projection range, that overlaps a part of thefirst projection range, from a second projection unit, first data fordisplay of the first image and second data for display of the secondimage are generated from data of the projection target image, wherein aregion of the first image, which is projected on an overlapping portionof the first projection range and the second projection range, isdefined as a first superimposed region and a region of the first imageother than the first superimposed region is defined as a firstnon-superimposed region, a region of the second image, which isprojected on the overlapping portion, is defined as a secondsuperimposed region and a region of the second image other than thesecond superimposed region is defined as a second non-superimposedregion, and the image processing method comprises a brightnessacquisition step of acquiring first brightness which is brightness ofthe overlapping portion in a state in which a specific image isprojected on the overlapping portion only from the first projection unitand second brightness which is brightness of the overlapping portion ina state in which the specific image is projected on the overlappingportion only from the second projection unit, and an image generationstep of generating data for projecting the specific image, as a firstportion in the first data for display, which corresponds to the firstsuperimposed region, generating a second portion in the first data fordisplay, which corresponds to the first non-superimposed region based onfirst input image data in the data of the projection target image, whichcorresponds to the first non-superimposed region, and the secondbrightness, and generating a third portion in the second data fordisplay, which corresponds to the second superimposed region based onsecond input image data in the data of the projection target image,which corresponds to the second superimposed region, and the firstbrightness.
 12. The image processing method according to claim 11,wherein, in the image generation step, a fourth portion in the seconddata for display, which corresponds to the second non-superimposedregion, is further generated based on third input image data in the dataof the projection target image, which corresponds to the secondnon-superimposed region, and the first brightness.
 13. The imageprocessing method according to claim 12, wherein, in the imagegeneration step, the second portion is generated by correctingbrightness of a pixel, which is less than the second brightness, amongpixels of the first input image data to the second brightness, the thirdportion is generated by reducing brightness of each pixel of the secondinput image data by the first brightness, and the fourth portion isgenerated by correcting brightness of a pixel, which is less than thefirst brightness, among pixels of the third input image data to thefirst brightness.
 14. The image processing method according to claim 12,wherein, in the image generation step, in a case in which the firstbrightness and the second brightness are equal to or less than athreshold value, the first input image data is regarded as the secondportion, the second input image data is regarded as the third portion,and the third input image data is regarded as the fourth portion. 15.The image processing method according to claim 13, wherein, in the imagegeneration step, in a case in which the first brightness and the secondbrightness are equal to or less than a threshold value, the first inputimage data is regarded as the second portion, the second input imagedata is regarded as the third portion, and the third input image data isregarded as the fourth portion.
 16. The image processing methodaccording to claim 11, further comprising: a projection control step ofperforming first projection control of projecting the specific image onthe overlapping portion only from the first projection unit and secondprojection control of projecting the specific image on the overlappingportion only from the second projection unit; and a brightness detectionstep of detecting the first brightness of the overlapping portion in astate in which the first projection control is performed and storing thedetected first brightness in a storage medium, and detecting the secondbrightness of the overlapping portion in a state in which the secondprojection control is performed and storing the detected secondbrightness in the storage medium, wherein, in the brightness acquisitionstep, the first brightness and the second brightness are acquired fromthe storage medium.
 17. The image processing method according to claim12, further comprising: a projection control step of performing firstprojection control of projecting the specific image on the overlappingportion only from the first projection unit and second projectioncontrol of projecting the specific image on the overlapping portion onlyfrom the second projection unit; and a brightness detection step ofdetecting the first brightness of the overlapping portion in a state inwhich the first projection control is performed and storing the detectedfirst brightness in a storage medium, and detecting the secondbrightness of the overlapping portion in a state in which the secondprojection control is performed and storing the detected secondbrightness in the storage medium, wherein, in the brightness acquisitionstep, the first brightness and the second brightness are acquired fromthe storage medium.
 18. The image processing method according to claim16, wherein, in the projection control step, the first projectioncontrol is performed a plurality of times by changing a set value ofbrightness of a first light source included in the first projectionunit, and the second projection control is performed a plurality oftimes by changing a set value of brightness of a second light sourceincluded in the second projection unit, in the brightness detectionstep, the first brightness detected for each of the first projectioncontrols is stored in association with the set value of the brightnessof the first light source in a state in which the first projectioncontrol is performed, and the second brightness detected for each of thesecond projection controls is stored in association with the set valueof the brightness of the second light source in a state in which thesecond projection control is performed, and in the brightnessacquisition step, from the storage medium, the first brightness and thesecond brightness which correspond to the set values of the brightnessof the first light source and the brightness of the second light sourceset when the projection target image is displayed are acquired.
 19. Theimage processing method according to claim 11, wherein, in thebrightness acquisition step, from the first brightness and the secondbrightness stored in association with each set value of brightness of afirst light source included in the first projection unit and a secondlight source included in the second projection unit, the firstbrightness and the second brightness which correspond to the set valuesof the brightness of the first light source and the brightness of thesecond light source set when the projection target image is displayedare acquired.
 20. A non-transitory computer readable medium storing animage processing program causing a computer to perform an imageprocessing method in which, for displaying a projection target image byprojecting a first image in a first projection range from a firstprojection unit and projecting a second image in a second projectionrange, that overlaps a part of the first projection range, from a secondprojection unit, the first image and the second image are generated fromthe projection target image, wherein, in the image processing method, aregion of the first image, which is projected on an overlapping portionof the first projection range and the second projection range, isdefined as a first superimposed region and a region of the first imageother than the first superimposed region is defined as a firstnon-superimposed region, a region of the second image, which isprojected on the overlapping portion, is defined as a secondsuperimposed region and a region of the second image other than thesecond superimposed region is defined as a second non-superimposedregion, and the image processing method comprises a brightnessacquisition step of acquiring first brightness which is brightness ofthe overlapping portion in a state in which a specific image isprojected on the overlapping portion only from the first projection unitand second brightness which is brightness of the overlapping portion ina state in which the specific image is projected on the overlappingportion only from the second projection unit, and an image generationstep of generating a black image as the first superimposed region,generating the first non-superimposed region based on a first inputimage of the projection target image, which corresponds to the firstnon-superimposed region, and the second brightness, and generating thesecond superimposed region based on a second input image of theprojection target image, which corresponds to the second superimposedregion, and the first brightness.